Range finder



J. MIHALYI RANGE FINDER June 4, 1946.

- Filed Jan. 19, 1943 10 Sheets-Sheet 1 PRIOR ART FIG. 1B.

48 Ca} V ZERO ADJUSTER M G H F FIG. 1

FIG. 2.

LIGHT DEV/ATUR 3. G I F JOSEPH MIHALYI INVENTOR BY June 4,1946. HAL2,401,700

RANGE .FINDER Filed Jan. 19. 1945 1o Sheets-Sheet :5

JOSEPH MIHALYI INVENTOR ATTY & A GT 'June4, 1946. J. MIHAL YI 2,401,700

= RANGE FINDER Filed Jan. 19 1943 1o Sheets-Shet-4 FIG. 7.

JOSEPH MIHALYI INVENTOR ATT'Y & AG'T.

J. MlHALYl RANGE FINDER June 4, 1946.

10 Sheets-Sheet 5 Filed Jan. 19,1943

JOSEPH MIHALYI INVENTOR BY W .ATT'YzfiAQT J. MlHALYl RANGE FINDER June4, 1946.

l0 Sheets-Sheet 7 Filed Jan. 19, 1943 JOSEPH MIHALH INV EN TOR W/M WM246* u gm Q EHQE 3 aw a 5 x EN June 4, 1946. J MIHALY] 2,401,700

RANGE FINDER Filed Jan. 19, 1945 10 sheets-sheet 9 FIG. 21A.

INVEN TOR We WM ATT'Y & AG'T JOSEPH MIHALYI 'June 4,-1946. J; MlHALYl2,401,700 RANGE FINDER Filed Ja'n. 19, 1943 10 Sheets-Sheet 10 FIG. 23A.

ATTY & AG'T' Patented June 4, 1940 RANGE FINDER Joseph Mihalyi,Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N, Y., acorporation of New Jersey Application January 19, 1943, Serial No.472,831

. 32 Claims.

1 This invention relates to range finders. This is Case A of a series ofpatent applications relating to this same subject, the other casesincluding the following:

Range finders-Case D Range findersase E Range findersCase F Rangefinders-Case G. Range finders-Case H. Range iinders0ase L. Rangefinders-Case J Range finders-Oase K. Range finders-Case L Pcilarizingbeam split- 472, 834 Jan. 472, 835 Jan. 479, 096 Mar. 479, 097 Mar.479,098 Mar. 479, 099 Mar. 479,100 Mar. 479,101 Mar. 479,102 Mar. 481,391 Apr.

Range finders-Case M. 491, 954 June Range finders-Case N. 491,955 JuneRange finders-Case O 491, 956 June Range finders-Case P 505,016 Oct.5,1943

Mihalyi, Tuttle. Mihalyi.

Holmes, Mihalyi. Mihalyi, MacNeille. MacNeille, Holmes. Mihalyi,MacNeille. Mihalyi. MacNeille.

Do. MacNeille, M ihalyi. MacNeille. MacNeille, Mihalyi,

The object of this invention is to eliminate entirely or reduce greatlythe errors in existing range finders. The main object of the inventionis to compensate for any distortion or deviation of the light pathsthrough the instrument due to such causes as mechanical stresses,strains, unequal thermal expansion and dislocation of parts due to shockreceived by the housing of the range finder. Although range finders mustalways remain relatively delicateflinstruments, the great,- est sourceof errors caused by non-rigidity is eliminated by the present invention.

It is also an object of one form of the invention to. provide means forreading the range directly in afield of view of the eyepiece of thefinder.

It is an object of one species of the invention to obtain some or all ofthe above advantages in a coincidence type range finders One form ofcoincidence range finder particularly discussed in this case, is th;symmetrical type having the comparison field approximately symmetricallylocated between the viewing points. Another type to which this case isparticularly directed involves the application of this invention tocoincidence range finders of the type sometimes known as D0. Mihalyi,MacNeille.

2 the scale, as well as to the broader aspects of the invention.

Since the present invention finds application in practically all typesof range finders, a brief outline is now given describing the featureswhich are common to all range finders to which the present invention maybe most readily applied. Range finders in general have two spacedviewing points or front windows at which they receive light, which issubstantially collimated, from the object being ranged. Simple ran efinders have been made without any lenses being involved, but thepresent invention is concerned with a refinement appropriate to andnecessary with only the more complicated systems which have at least oneobjective in both beams or one or more objectives in each beam. Theoptical system of any range finder on receiving the two beams of light(called the object beams) directs them by reflectors near one or both ofthe viewing points to form images in comparison planes which may beseparate as in stereo range finders or may be co-planar as in variouscoincidence type range finders including split field, superimposedfields, etc. A range finder usually involves some form of range adjustersuch as a light deviating means which is useful in either stereo orcoincidence type range finders or reticle movingmeans which is usefulonly in stereo type finders. The broad invention as described in thiscase is not primarily concerned with the forms which these standardfeatures may take in various range finders. It is noted that in eachtype part of the optical system of a range finder operates only on oneof the object beams and another part of the optical system operates onlyon the other object beam. There may also be a ortion of the systemoperating on both objectbeams but this portion is not so critical to thepresent invention. This point ismentioned because the present inventionis specifically concerned with correcting for errors in the independentportions of the optical system as thus defined.

According to the present invention standard range finders are improvedby incorporating into thema pair of adjustment coindicant elements suchas a scale and index or as specifically described in Case E a fiducialmark and adjustable coincidence line. The scale and index may be simpleor have a relatively complex form. Also, according to theiinventiommeans are included for projecting through at least the exact opticalequivalent of both of the above described portions of the optical systemlight from one of the elements into focus'forming an image adjacent tothe other element or an image thereof. In one form of the invention,described in more de tail in a Case I-I, light is projected from bothelements forming images adjacent to one another in a third plane. Inevery form, however, the image formed by light projected from at leastone of the elements is adjacent to the other element or an imagethereof, This light beam from one element to the other is referred to asthe element beam to distinguish it from the object beams.

The ranging adjustor of the range finder also adjusts this element imagerelative to the adja cent entity whether it is the other element itselfor an image of the other element.

In one preferred form of the invention, the elements are in thecomparison planes or at least optically in those planes. That is, theymay be to one side of the planes but a mirror directing light into thesystem is positioned so that it forms a virtual image. of the elementsin the comparison planes. This means that the elements are at leastoptically in the field er view of the eyepiece, and hence, in this formofthe invention it is quite simple to provide means for reading therange directly through the same eyepiece. i

Preferably th adjustment coindicant elements, e. g; the-scale and.index, are rigidly attached to the means for defining the. correspondingcomparison planes or are rigidly attached to one another in' the case ofa coincidence range finder.

In one preferred form of the invention, the index is the element whoseima e is projected adjacent to the scale and this has the advantage ofsimplification, but inanoth'er form of the in vention, "describedinIIfior'e detail in a Case P. the scale i the element projected, theindex being fixed. In fact, in Case F this latter feature is combinedwith the fiducial mark and coincidence line form or adjustmentcoin'dicant elementstogive other advantages.

, Additional objectives may be included in preferred forms of theinvention for collimating and/or. refocusing the light in the elementbeam. Of course, it is simpler to have the elements at least opticallyin the comparison planes and to form'the' image of one adjacent to theother, but froma purely 'theoretical'viewpoint the elements could beslightly out of these plane as long as theyiare *conjugate to oneanother and the light forming the image of one element adjacent to thebthersufiers all'of the deviations of the range finder-system;- v

- The theory of the'present invention is that any error introduced inthe range finder-system which error-g'mov'esone "or the object imagesrelative to thewother, similarly displaces the adjustment inclicantelement image relative to the other adjustment 'co'indicant "element.Thereforelwhen behind each'yiewing point to reflect. the object bea stoward t (E ter of the instrument where it is received by crossedreflector and directed into comparison planes. In any form of rangefinder, the present invention can, for example, be applied by placing asmall, or a large semitransparent, optical square in front of theviewing point to receive the element beam from the main reflector. Thesesmall orsemi-transparent reflectors then reflect the element light beamfrom one viewing point to the other and back into the optical system ofthe range finder eventually to reach the comparison plane or its opticalequivalent adjacent to the other adjustment coindicant element. Someform of auxiliary reflector is usually required to direct this lightfrom one viewing point to the other. If in a coincidence range finder atransparent element is included having a hat surface for defining thecomparison planes, it is convenient to have the adjustment coindicantelements on this fiat surface or on an equivalent one. When thusarranged in the field of View of the eyepiece, it is preferable to havethe elements at the margin or the field so as not to interfere with theobject images being brought into coincidence. Some range'finders havethecomparison plane at an angle to a fiat surface of an optical elementwhich surface has areflecting area divided from a transparent area bythe line of intersection with the comparison plane. In such finders, onepreferred form of themvention has one of the'ele'me'nts in the form of atransparent marking in the reflecting areap eferably near the dividingline. Light is then sent from behind this reflecting surface throughthis transparent marking not toward the eyepiece but back toward theranging system as required to form the element light beam. This systemprovides a convenience inthat the source of light to illuminate theadjustment coi'ndicant element, is on the opposite side of thecomparison plane from the eyepiece. For example, when. the re fleetingplane is formed between two right angle prisms to be viewed through thehypotenuse of one of the prisms, a light source may convenient- 131 belocated to send light through the hypotenuse faeeoi theother rightangleprism.

The invention is applicable directly "to orthops'eudo "stereorahg'efinders since, except for the fact that ein-ciaenee is obtainedindep'th, these may be t'rea ted'exactly asother coincidence'rahgefinders. oreou'rs the comparison planes are usually separate butsince'i'n this case, light traV- ls from one plane to thef'other,"theadjus'tment coi'ndicant eiementsmay be iil'ftlfe separate plane's orpreferably 'bothin'oneplane;'. r

Other advantages and the for producing them will be fully understoodfrom" the-renowing detailed "description bf the inventiiinyvhen read'eonnection with the accompanying drawings in which: I I Fig-. *1illustrate'sthe closest pner art. Figs.

. l- A ar-id 1 B showing'altersaitive views thi teen fth'e eyepiecerespeetivei 'w eiitestin 'andwheniaiig ---Fig' 2-'shoWs an opticalsystem illustrating the reeds-m anal dinerencesbi the invent on-from thetrier an, Fig. 2A is a view through the eyepiece of'tfie instrument s inFig.2

JFiEi'B snows a prism arrangement alternative to t a shown asa detail ofFi'g-2.

' Fig. 4 illustrates-the optical system of an embeeiment oftheinventionalternative to that shown in Fig.2. 7

i e 15 similarly illustrates stillf'another em sediment er theinvention, Figs. snanutn'show ing the respective views through the twoeyepieces of the system.

Fig. 6 is a perspective view f a preferred embodiment of the inventionas applied to symmetrical type coincidence range finders, Figs. 6A andSBshowing the respective views through the eyepiece without and with theauxiliary finder system. 1 r

Fig. 7 is aplan, partly in section, of the range finder whose opticalsystem is shown in Fig. 6. Fig. 7A shows a vertical section of thecoincidence prisms of Fig. 7. h

. Fig. 8 illustrates in detail the scale and index fthe instrumentillustrated in Figs. 6 and'I.

Fig. 9 is a perspective view of the optical system of another preferredand simplified embodiment of the invention, Fig. 9A showing the viewthrough the eyepiece of this embodiment.

Fig. 10 shows a horizontal section of a range finder having the opticalsystem illustrated in Fig. 9.

Fig. 11 shows an alternative arrangement of the scale and index of theoptical system shown in Fig. 9, Fig. 11A being a view through theeyepiece when this alternative arrangement is used.

Fig. 12 shows the perspective of the optical system of a stereoscopicrange finder incorporating the invention and for clarity is enlarged sothat the two parts of the figure appear on different sheets of thedrawings. Thesymmetry of the instrument allows the invention to be fullyunderstood from either part of Fig. 12. Fig. 12A shows the views throughthe binocular eyepieces of the instrument. Fig. 12B shows the viewthrough the scale reading eyepiece of the instrument.

Fig. 13 is a horizontal section of a range finder incorporating theoptical system of Fig. 12.

Fig. 14 shows a similar range finder which differs from Fig. 13 byemploying as the ranging adjuster, means for moving one of the recticlemarks relative to the other instead of a light deviating device.

Fig. 15 shows the optical system, in perspective, of an ortho-pseudostereo range finder incorporating the present invention. Fig. 15A is avertical section of a. detail of Fig. 15. Fig. 15Bis a similar sectionof an alternative arrangement.

Fig. 16 differs from Fig. 15 by incorporating the present invention in amanner which permits the scale to be read in at least. one of theeyepieces used for observing stereo coincidence. Fig. 16A shows the viewthrough the binocular eyepieces of this range finder.

Fig. 17 illustrates in perspective an alternative embodiment of theinvention.

Fig. 18 is a plan view of the arrangement shown in Fig. 17. V

Fig. 19 is a vertical section of a detail of the arrangement shown inFig. 17.

Fig. 20 shows the optical system for another embodiment of theinvention, Fig. 20A being a view through the scale reading of theeyepiece of the system. Fig. 20B illustrates a detail of the arrangementshown in Fig. 20.

Fig. 21 illustrates in perspective a preferred embodiment of' theinvention using a fiducial mark and coincidence line according to thepresent invention combined with an arrangement for permitting the scaleand index to be viewed in the eyepiece of the system as illustrated inFig. 21A.

Fig. 22 is a horizontal section of a detail of the arrangement shown inFig. 21.

arrangement whichever is. more In Fig. 1 is illustrated the opticalsystem of knowntypes of range finders.

When ranging a subject, light is received at the two spaced viewpointsand directed by the penta-prisms or optical squares 49 throughobjectives 4| to ,crossed mirrors 42 to be brought to focus incomparison planes which in this case are coplanar at the surface 45 of asplit prism 43 having a semitransparent reflector 44 at the diagonalsurface thereof. Theseimages are viewed through. an eyepiece 46 by theeye 41 of an observer who, when viewing an airplane sees an arrangementsuch as shown in Fig. 1B or perhaps a full field convenient. Theseimages in the comparison planes are brought into coincidence by a lightdeviator 5|. In case the instrument gets out of adjustment, it maybechecked by observations of an artificial infinity. This is provided byturning on a light 48 to illuminate a mark 49 whoseimage is projected bythe semi-reflector 44 into one-half of the range finder system. Sincethe mark 49 is optically at the same distance from the objectives 4! asthe surface 45, this light fromthe source 48 is collimated by one of theobjectives 4| and passes into adjacent penta-prism 40 and out throughthe frontwindow or viewing point of the instrument. However, whenchecking the instrument, two auxiliary penta-prisms 52 are swung intoplace as shown so they reflect the light from one viewing point to theother and back into the range finder. This light thus refiected isbrought to focus by the other objective ll forming an image 49' in thefocal plane of the eyepiece 46, ie. at the surface 45. This surface 45is provided with a mark 50 which by comparison with the image 49'indicates when the'instrument is in proper adjustment. If the instrumentis out of adjustment, a zero adjustor 53 is operated to bring the image49 into coincidence with the mark 50. v

Such an arrangement has proven in practice to have severaldisadvantages. In the first place, it is not possible to use the rangefinder when checking its zero adjustment. In the second place, thefinders often due to a slight bump, get out of adjustment immediatelyafter makinga zero correction. In fact, the only safe way to take arange with such an instrument is to correct the zero immediately beforeranging and then to check the instrument after ranging, accepting thereading only if the instrument is shown to have remained in properadjustment. Obviously, such a range finder if it gets out of adjustmenteasily is practically worthless when attempting to make split-secondrange readings necessitated by modern warfare. In the third place, thecheckin of the zero adjustment involves the use of a movable auxiliaryoptical system which itself may therefore get out of adjustment.Incidentally, it is not convenient to have the range scale in theeyepiece of such an instrument because of the preferable position of thelight deviator, such as shown.

According to the invention as shown in Fig. 2, on the other hand, sucharange finder may be improved by having the scale and index mounted inthe eyepiece field or at least optically in this field. In thisarrangement the light from the objective being ranged is received byoptical according to the invention this light is received by a smallpenta-prism l2 cemented to the'front of the large penta-prism 6i! and isthence reflected to-the' other viewpoint of the system to be received by"a similar small'penta-prisrn l2 and c v 8 being reflected from'thevicinity of one range finder viewing point to the other, passes throughthe other portion of the optical system used for forming the otherobject image in the comparison fields. optical system-between thecrossed mirrors 62 and Q the focal plane of the eyepiece S B-is commonto reflected back into the other portion of the range finder opticalsystem. This collimated light is then brought to focus by the objective6| forming an image 69 at one margin of the field of the eyepiece 66 asshown in Fig. 2A. A scale 10 is inscribed on the surface 65 in thisiocal plane against which scale the image 69 indicatesthe range of theobjective being tested. The light beams from the external target intocoincidence.

' from the objective in one of the beams is adjusted by a light deviatorH to bring the two This light deviator ll simultaneously and similarlyadjusts the element light beam coming from the index 69.

It will be noted that the scale of the light de- "viator 1| is no longercoupled directly to this element of the instrument in this particularembodiment of the invention. Similarly, there is no zero adjustercorresponding to element 53 of Fig. 1 although some adjustor may beincluded for other purposes such as fieldhalv'ing. Furthermore, theauxiliary penta-prisms 12 remain in place at all times and are not swungto one side. The advantage of the invention is that no matter whathappens in the optical system of the range finder to cause the images ofthe object being. ranged to move relative to one another, the

same deviation is introduced into the beam of light forming the image E9so that the reading .is still correct. For example, suppose one of theobjectives .iil is knocked slightly sideways causing the object image tobe shifted similarly side- Ways. This moves the image 6.9 an equaldistance to one side; When the instrument'is adjusted by the lightdeviator H to bring the two object images into coincidence the image 69,read against the scale it, gives .the correct range automaticallycompensating for any errors in the optical system.

In Fig.3, the penta-p'risms 611 and '12 are replaced by a .Denta-prism15, the samesize. as the penta-prism cemented to an equal sizepentaprism 76 having a third prism Tl cemented to the front surfacethereof with a semi-transparent,

semi-reflecting surface 18 therebetween. This permits the light from theobject to pass unhindered through'the' prism TI and 16 into the prismi5, except for the diminution ofintensity by the surface 78.Light-from'the index 69', however, passing from the'prism "55 into theprism 15 is partly reflected by the surface 18 to operate in thesamermanneras in Fig. '2.

Fig. 4 diflers from Fig. 2 by using a single more powerful objective 80in place of the two objectives 6!, which has certain advantages andcertain disadvantages, This figure is included to illustrate the 'factthat the light from the index 69 passes through the portion of the.optical system which forms one of the object images .or the exactoptical equivalent thereof and then after dex and scale partoi thesystem is quite '-inde-' pendent of the comparison'fieldhalf of thesystem. The-crossed mirrors 81 in this case-are reflecting-from eitherside-so that in one-case they send light from the object being rangedthrough the objective to form images-as seen in Fig. 5B. In thisarrangement,- an auxiliary objective 82 is provided on the side of thecrossed mirrors '8 opposite to the objective 80. Such arrangements arediscussed in more detailin Ca-se D of this series. Light froin a source-81 is reflected by a totally reflecting pris-m'BB to ill-umi- 'nate anindex 88 engraved on aplate 83 placed atthe focal planeofth'eobjectiVeBZ. Light from this index '88 which may be "eitherabla-ck mark on a transparent ground or-a transparent mark on a darkground'is collimatedby-the objective 32 and the col-limated light isreflected byvthe back of one of the crossed mirrors 8-l into-the rangefinder optical system'headi-ng toward'one of thempenta-prisms l5. Thiscollimated light after the round trip from eneran'ge finder View ingpoint to the other is reflected by the other of the crossed mirrors 8*!back through the objective 82 and is brought to focus forming anim-age88' in the plane 83-which may be read against a scale 89 by meansof an eyepiece 84; and theye 85 of a second observer. In this case; thein strument is a-two-man range finder. Since anythat the adjustmentcoindicant element beam 7 traverse this part of the range finder system.The same is true of anything which affects the deflection of the lightpassing from the index 88 to' the mirrors 85 since the effect would becounteract ed by thecorresp'ondi'ng effect on the reading beam formingthe-imageflfi'f At this point. it is noted that the objectives '8!) and82 need not have the same power. lhe important point is that the lightforming the image of the adjustmentcoindicant element, in this case theindex, must traverse all of the portions of the range finder opticalsystem which operate only on one of the beams. Anything which happens toeither of the object beams'up to the time at which they are togetherentering the objective 8'!) could introduce an error. However, theeffect would be exactly the same onthe light from the index 88.

For example, if one of the mirrors 8! is rotated responding part of theobject imageas seen in Fig. 5B is shifted to'one side. Simultaneouslythe image 88 is moved along the scale 89 as seen in Fig. 5A. When thisdeflection, which in an ordinary instrument would cause an errorin tli'ereadingis automatically corrected by movingzthe light dev'iator to bringthe images in Fig. 53 back into coincidence, the index 88' on the scale89"is' It will be noted that the portion'ofthe 9 brought back to thepoint at which the correct reading is given.

Figs. 6, 7, 7A and 8 illustrate a symmetrical type range finderincorporating the invention as well as an auxiliary finder system morefully described in Case G. penta-prisms 69 and 12 as well as theobjective 6| correspond to those of Fig. 2. The crossed mirrors arereplaced by crossed prisms 90 and 9| mounted one above the other. Sothat the light reaching the prism 99 from corresponding objective' 6|will be symmetrical to that reaching the prism 9|, an auxiliary rhomb 92is cemented to the-prism 99 to shift the entrant beam upward. The lightreflected from these two prisms 90 and 9| enters two right angle prismswhich in the embodiment shown happen to be 39-6399 prisms 93 and 94.These two prisms are cemented together and to the prisms 90 and 9|; thelight from the crossed prisms 99 and 9I is reflected at the hypotenuseof the prisms 93 and 94 toward the horizontal contained surface part 96of which is reflecting and part 91 of which is transparent. Thelinebetween surface parts 96 and 91 lies in the coplanar comparison planes(I III shown in Fig.7A) of the range finder and is viewed through thehypotenuse surface of the prism 93 by means of an eyepiece 95. Lightfrom the prism 90 as reflected by the hypotenuse surface of the prism 93is reflected again and through the eyepiece 95 by the reflecting portion96 of the comparisonfield. Light from the prism 9! on the other hand asreflected by the hypotenuse surface of the prism 94 passes to theeyepiece through the transparent area 91. According to a preferredembodiment of the invention, an index 99 consisting of a transparentmark in the reflecting portion 96 of the comparison field is illuminatedby a light source I91. Light from this index 99 passes up through theprism, is reflected into the prism 99 and by the prism 92 is directedthrough the objective GI and prisms 69 and 12 going from one viewingpoint to the other as a collimated beam and back through the otherobjective iii to the prisms 9I and 94 to form an ple, by moving thecenter prism unit. horizontally and transversely with respect to thebase of the range finder, the image 99' moves along the scale 98. V

These Figs. 6 and '1 incidentally illustrate the auxiliary view findersystem of Case G as applied to a symmetrical type range finder. A lensI9! is provided which is of shorter focal length than the objectives 6|so that light from the object being ranged passing through the lens HMand reflected by removable mirrors I92 to the comparison plane forms areduced image I93 as shown in Fig. 63. Of course, the lens IDI isoptically nearer the comparison plane than the objectives 6 I. As bestseen in Fig. '1 the mirrors I92 are pivoted at the point I94 so thatthey may be swung into or out of range finder beam. In practice, oneholds the mirrors in the beam just long enough to bring the object to beranged into the field of View at which time it is seen as a small imageI93 by itselforqwith a larger pair of In this arrangement, the

10 images showing at least partly due to the objectives BI. The mirrorsI02 are then moved out of the optical system so that no light throughthe lens IOI reaches the comparison plane and the range finder is usedin its normal way.

Fig. 7 shows the housing I in addition to the optical system discussedin connection with Fig. 6, and Figs. '1 and 7A illustrate the convenientmethod employed for moving the prism unit including prisms 99 and 9|transversely to give relative movement of the object images. Rotatabledisk I06 is provided with a cam or spiral slot engaging a cam followerI98 so that rotation of the disk I09 causes prism unit carried by thecam follower I98 to move transversely as indicated by the double-headedarrow I99.

In Figs. 9 and light from theobject being, ranged through the twoviewing points is r'e flected by amirror I29 and a semi-transparentmirror I2I through an objective I22 and an erecting prism I23 to formimages I25 as seen in Fig. 9'

in a comparison plane defined by a transparent member I24. These imagesmay be viewed by the eye I21 of an observer through an eyepiece I25. Toadjust one of the images transversely to bring it into coincidence withthe other the mirror I29 is mounted to rotate about a vertical axis at apivot point I29. This movement is provided by any suitable means such asa nut and driving screw I28. According to the invention, an index I31engraved on'the disk I24 is illuminated bylight I and a reflecting prismI3I. Light from this index as shown by the light ray I312 passes throughthe erecting prism I23 andobjective I22 to become collimated and pass toa reflecting surface I 33 mounted rigidly on the mirror I20. This lightis then reflected as shown by the ray I34 through a dove prism I35rigidly attached to the mirror I H and then as shown by the ray I39enters the objective I22 to be brought to focus forming an image I31adjacent to a scale I38 engraved on the disk I24. Of course, anymovement of the objective I22 affects both object images in the samemanner and does not'introe duce any error. Any movement of the mirrorI29 whether due to the adjusting screw I 28'or to some external cause isaccompanied by asimilar movement of the reflecting surface I 33.Similarly, any movement of the mirror I2I is accompanied by anequivalent movement of the dove prism I35. Therefore, anything whichaffects the relative position of the two images I25 as seen in the fieldof view affects in exactly the same way the image I31 relative to thescale 138. When the two images I25 are brought into exact coincidencethe scale and index give the correct range independent of the adjustmentof the various parts of the system. The dove prism I35 may be arrangedto intercept the returning beam I34. as shown or to intercept theoutgoing portion I32 of the element beam, the scale I38 being calibratedaccordingly. Fig. 10 shows this same optical system together with itshousing I149 having front windows therein to constitute the View! ingpoints of the range finder.

Figs. 11 and 11A difier from Figs. 9 and 9A by the use of an obliquescale and index. In this case an oblique index I42 is illuminated by alight source I and light therefrom is reflected by atotal reflectingprism I43 into the erecting prism I23. This light travels through theoptical system as in Fig. 9 and ends as an image I4 of the index I42lying at an acute angle to the scale I which consists of a series ofdots. Slight lateral movement of the index image I44 gives a relativelylarge movement of the point ofintersection with the scale I45 whichresults in greater sensitivity and ease of reading. In this 1 1 theindexI42, prism I43 and focal plane carrying the scale I45 are all shown forclarity as separated from the erecting prism I23. It is oftenconvenient, as described in Case B, to have the index I42 andthe scaleI45 engraved right on the surface of the prism- I23 and to have thelight from the lamp I II pass through the reflecting prism I 43 beforeit illuminates the index I 42. Of course, this permits the eyepiece I26to be much closer to the erecting rism I23 whose surface constitutes thecomparison planes.

In Figs. 12-, 12A, 12B and 13, a stereoscopic range finder is shownhaving front windws I50 through which light is received from the objectbeing ranged and. is then reflected by optical squares consisting ofmirrors I5I through objectives I52 into focus in comparison planes I53which are quite independent of each other in this stereo finder. Bymeans of relay lenses I54, erect ing prisms I55 and rotatable rhombs I50to permit different interccular separation of the eye'- pieces I51,images are formed in the focal planes of the eyepieces I51 to be viewedby the right and left eyes I58 of an observer. The image planes I53 areprovided with reticle marks I as best seen in Fig. 12A and due tostereoscopic fusion these reticle mark-s appear to be at some fixeddistance from the observer. Lateral movement of one of the object"images in its image plane I53 without a corresponding movement of theother object image causes the object to appear at a different distance.-Such lateral movement is provided by a light deviating device I68 whichisadjusted until the object appears to be at the same distance as thereticle marks I10. In an ordinary stereo range finder,- the deviationmight be index traverses the whole of the pertinent optical system,itcorrects for errors occurring.- i this system. It will be noted in everycase, the image of one of the adjustment coindicant elements is by thepresent inventionbrought adjacent to the other adjustment coindicantelement or as discussed above adjacent to the image thereof.

Fig. 15 shows an ortho-pseudo stereo range finder which for manypurposes may be cons-idered a coincidence range finder in which thecoincidence is match in depth. Light from the object being ranged, whichin this case is indicated by odd shaped block I80, enters the viewingpoints of the range finder and is reflected by mirrors I8-I throughobjective-s. I32 to form inverted images I84 in the comparison planes ofthe system. The little blocks I50 are, of course, only representative ofthe. beam of light coming from the real object being ranged, which is ata great distance. By means of rhombs I9I and the half lens I92, lightfrom the images I 84 passes at least partially to form erect images I93immediately below the images I84. That is, an erect right viewing pointimage is formed below an inverted left viewing point image and viceversa. Both of these images are then viewed byrelay lenses. I85 and I86,erecting prisms I81, eyepiece prisms I88, and. eyepieces I89.Ad-justmento-f the light deviator I95 causes the right viewing pointimages to move laterally with respect to the left viewing point imagesso that the inverted fused,

image seen in the eyepiece appears to move axially away or toward theobserver at-the same time as the erect fused image appears to move inthe opposite direction. This gives the wellknown and spectacular eflectof the crtho-pseudo range finder. The coincidence is judged when w theerect and inverted images appear to be at the tive I52 to form an imageI6I' as shown in Fig.

12B adjacent toa scale I 64 engraved on the other comparison plane I53.This scale and index image is viewed by means of a reflecting prism I65and an eyepiece I66 by a'second'o-bserver whose eye is shown at I 61 andwhose field of view is shown in Fig. 1213, It will be noted that thelight from the index I6I to formthe image I 6 I passes through the twoportions of the optical system which independently form the images inthe comparison planes and also by means of penta-prisins I62 and I 63,from one viewing point to the other. Fig. 13 shows the housing I1I fortheinstrument, in which housing the two front windows I50 are mounted.

In Fig. 14 the light deviator I68 is eliminated and this is replaced bymeans I12 for moving one of the reticle marks I10 laterally so that theapparent distance of the markjis made to change to match that .of theobject. This movement is accompanied by a similar movement of the scaleI '64 cemented to the disk I53 carrying the reticle mark I10, and hence,the range ma be read directly, As before, since the light forming thesame distance from the observer. As shown in Fig. 15A the comparisonplanes are provided with field lenses I and the lower half of eachcomparison plane is reflecting so that the erect images may be viewed inthe eyepieces of the system, 7

According to the invention, an index I96 i1- luminated by a light I ismounted in one of the comparison planes and light therefrom collimatedby one of the objectives I82-is reflected by mirrors I8I, penta-prismI31, penta-prism I98 and the other mirrors I8I through the lightdeviator I 99 and the other objective I82 forming an image I99 adjacentto the inverted image I84.

This image I99 by means of rhombs ISI and lens I82 is refocused as animage 200 adjacent to a scale 20I below the reflecting part. of theadjacent comparison plane. By means of an eyepiece 202 a second observerwhose eye is shown at 203 may read the ran e from this scale.

Fig. 15B shows an alternative arrangement in which therhombs I SI arereplaced by rhombs whose sides are not parallel but which receive thelight at a slight angle and pass itthrough the center of a lens 2I6(rather than through the- The ar-' 13 the other comparison field at thepoint 201 without any apparent image being seen therefrom and throughthe objective I82, the mirrors I8I to the penta-prism I98, and thence tothe other penta-prism I97 and back into the optical system of the finderto form an image 258 adjacent to a scale 269 engraved on the samecomparison plane field lens as theindex 205. This scale 209 and image208 are visible in the left eyepiece, as shown in Fig. 16A, at thebottom thereof below the image I84 which due to the erecting prisms andeyepieces, etc., appears to be upright in this left ey field. Of course,images 2H) and 2H of this image 298 and scale 209 are visible in theright eye field since they are formed by the lens- Fig. 17 differs fromFig. 4 mainly by having both adjustment coindicant elements illuminatedand light therefrom projected through the range finder optical system toform images adjacent to one another in a third plane. As before theimage of one of the elements falls adjacent to at least an image of theother element. The index and scale are engraved on a plate 222 in thecomparison field and are illuminated by lamps 224 and 225 whose light isdirected by reflecting prisms 226 past the adjacent element to the lens80 whereat it is collimated. These collimated beams are then reflectedby the crossedprisms 220 to the pentaprisms Gil and I2 and back toreflecting surfaces 221 as best seen in Fig. 19 and thence upwardthrough a lens 228 to be brought to focus adjacent to one another in theplane 229 forming images 230 and 23I giving the range to be observed byeye 232 of an auxiliary observer. Anything which affects the two imagesin the comparison plane 222 equally affects one or other of the lightbeams from the elements engraved thereon so that the displacement of theimages 230 and 23I relative to each other compensates for any errors inthe system.

Fig. 20 shows a corresponding modification of Fig. in which a scale 238and index 231 (see Fig. 20B) are engraved on a plate 238 positioned atthe optical equivalent of the focal plane of the eyepiece 65. Theseadjustment coindicant elements 231 and 238 are illuminated by a lamp'235and light from the elements reflected by the backs of the cross mirrors3| is collimated by the objectives SI and then reflected by prisms 235at which light from the object being ranged is received in the usualway. These two beams of light are then reflected forward to thepentaprisms 239 which reflect them parallel to each other through anobjective 249 into focus superimposed, as seen in Fig. 20A, on an imageplane 2 iI to be viewed by an eyepiece 232. It will be noted that thescale and index are rigid to one another on the member 236 which is inthe optical equivalent of the focal plane of the eyepiece 65 and thatlight from the two beams traverses all of both portions of the rangefinder system which portions operate independently on the two beams fromthe object being ranged or at least the optical equivalent of these twoportions since the light is reflected from the back of the mirrors BIinstead of from the front.

In Figs. 21, 21A and 22 is shown an arrangement alternative to thatshown in Fig. 9., which alternative arrangement has a fiducial mark andcoincidence line as the adjustment coindicant elements rather than ascale and index. The simpler forms of this are described in Case E andthis more complicated form as shown in Fig, 21

a combination of the advantages of a fiducial mark and coincidence linewith a scale also visible through the system. It will be noted in thiscase that the scale and not the index is the element projected and thatthe coincidence line is the important element which is projected, thefact that the scale is visible being only incidental. This arrangementin Fig. 21 differs from that in Fig. 9 by having the mirror I20 adjustedby a cam 255 which is rotated on a bar 254 by a cam follower 253 ridingon a cam 252 rotated by the ranging knob. This knob simultaneouslythrough a bar '25I rotates a coincidence line 256 consisting of a spiralon a disk 25!] which coincidence line is illuminated by a light 258 andis projected through the erecting prism I23 and objective I22 to bereflected at the surface I33 and the dove prism I35 to form an image 259between two fiducial marks 269 appearing in the margin of the comparisonplane I24.

In the simplest form of fiducial mark and coincidence line theinstrument would be adjusted perhaps as in Fig. 9 by screw I28 and thenthe disk 250 carrying the coincidence line 255 would be rotated untilits image 259 fell between the fiducial mark 250 at which time the rangecould be read from any convenient scale mounted on the disk 250. Thereading would be by some second observer. However, by the arrangementshown in Fig. 21, the adjustment of the mirror I20 rotates the spiral256 to keep it in proper adjustment at all times. As long as theinstrument is in proper adjustment the scale 251 adjacent to the indexline 256 may be read as shown in Fig. 21A by any index, the fiducialmarks 260 serving this purpose as well as any other. If anything shouldhappen to the instrument to get out of adjustment the coincidence lineimage 259 will no longer appear between the fiducial marks 260 and therewill not be automatic correction of the reading because the spiraliselongated so that this transverse movement is not along the scale. Ofcourse, one could take hold of the disk 25% and rotate it independentlyof the adjustment of the mirror I28 and bring the right part of thecoincidence line between the fiducial marks ZBO at which time thereading would be correct, but it is more convenient to adjust the mirrorI2I as by a ment gets out of adjustment it is immediately apparent tothe observer since the line 259 is no longer between the fiducial marks260 and he adjusts the cam 25! to bring the line back to its properposition. He then may take a reading directly by adjusting the rangeknob since after the instrument has been brought into proper adjustmentit will stay in adjustment while he makes a reading or will indicate themovement if it gets out of adjustment.

Figs. 23 to 26 are very similar to Fig. 21 but have somewhat differentarrangement of the var ious parts. 'The mirror I25 is adjusted by alever 21'! through a connecting rod 276 which is operated by a camfollower 275 riding on a horizontal cam 215 which may be turned by ashaft 273 con nected to the range knob not shown. The disk 279 alsorotated by this shaft 273 carries a spiral and scale 212 which isilluminated by a light 211 through a prism 2'58. This light passesdownward through the disk 2l9 to a prism 282 whence it is reflected by aForm prism 28| and an erecting prism 21!] and thence through the opticalsystemas before, coming to focus in a comparison plane 21'! forming animage adjacent to fiducial marks 263 as best seen in Fig. 23A. Thiscomparison plane 2l'l i viewed by an eye I21 and eyepiece I26 as before.In Fig. 23 the mirror I2! is adjusted by a nut and driving screw 282instead of by a cam. Otherwise this Fig. 23 is similar to Fig. 21 butthe more complex optical system as best illustrated in Figs. 24, 25, and26 is introduced to give an instrument much more convenient to use.

Having thus described various preferred embodiments of my invention, Iwish to point out that it is not limited to these specific structuresbut is of the scope of the appended claims.

What I claim and desire to secure of Letters Patents of the UnitedStates is:

l. A range finder of the type having two spaced viewing points at whichsubstantially collimated beamsof light are received from the objectbeing ranged, an optical system including reflectors at each viewingpoint and at least one objective for directing and focusing the objectbeams to form images in comparison planes and a ranging ad: luster,characterized by a secondary reflector permanently located at a pointsubstantially in the object beam at eachviewing point, for reflectinglight from one viewing point to the other, a pair of adjustmentcoindicant elements and means including the secondary reflectors, forprojecting While ranging, a light beam from one of the elements throughat least the optical equivalent of said optical system for formingimages and from one viewing point to the other to form an image of saidone of the elements adjacent to at least an image of the other element.

2. A range finder of the type having two spaced viewing points at whichsubstantially collimated beams of light are received from the objectbeing ranged, the optical system including at least one objective, fordirecting and focusing the two collimated object beams forming images incomparison planes, one portion of the optical system operating only onone of the beams and another portion operating only on the other beamand a rangin adjuster, said range finder being characterized by asecondary reflector permanently located at a point substantially in theobject beam at each veiwing point for reflecting light from one viewingpoint to the other, a pair of adjustment coindicant elements and meansfor projecting while ranging and through at least the exact opticalequivalent of both of said portions, a light beam from at least one ofthe elements into focus forming an image of said one element adjacent toat least an image of the other element.

3. A range finder of the type having two spaced viewing points at whichsubstantially collimated beams of light arereecived from the objectbeing ranged, an optical system including at least one objective, fordirecting and focusing the two collimated object beams forming images incomparison planes, one portion of the optical system operating only onone of the beams and another portion operating only on the other beamand a ranging adjuster, said range finder being characterized by a scaleand an index constituting a pair of adjustment coindicant elements andmeans for projecting through at least the exact optical equivalent ofboth of said portions and while ranging, a light beam from at least oneof the elements into focus forming an image of said means are includedfor defining the comparison planes, said elements are at least opticallyin the corresponding comparison planes and are rigidly attached to thecorresponding plane defining means.

7. A range finder according to claim 3' in which said elements are inthe corresponding comparison planes.

8. A range finder according to claim 3 in which said projecting meansprojects said one element image adjacent to the other element itself.

9. A range finder according to claim 3 in which an eyepiece is includedfor viewing the comparison planes and at least images of said scale andindex are visible through said eyepiece.

10. A range finder according to claim 3 in which said projecting meansincludes an objective other than those in said optical system, forcollimating the light from said one of the elements.

11. A range finder according to claim 3 in which every part of theoptical system which deviates one of the object beams relative to theother also deviates the element light beam correspondingly and withequal rates of change in beam direction.

12. A range finder according to claim 3 in which said projecting meansincludes a small optical square permanently located at points near eachviewing point oriented to reflect light from the adjacent system portiontoward the other square while ranging.

- 13. A range finder according to claim 3 in which said projecting meansincludes a semitransparent reflector permanently located at points neareach viewing point oriented to reflect light from the adjacent systemportion toward the other reflector while ranging.

14. A range finder according to claim 3 in which said optical systemincludes amain reflector at each viewing point and said projecting meansincludes an auxiliary reflector attached to each main reflector, eachauxiliary reflector being oriented to reflect light from the adjacentmain reflector toward the other auxiliary reflector.

15. A range finder according to claim 3 and of the coincidence type inwhich said comparison planes are coplanar, the ranging adjuster is alight deviating device and ranging is done by adjusting the objectimages into register.

16.A coincidence range finder of the type having two spaced viewingpoints at which substantially collimated beams of light are receivedfrom the object being ranged, an optical system for aligning the twoobject light beams, for directing them toward a comparison plane and fordeviating one beam relative to the other, said range finder beingcharacterized by secondary reflectors respectively and permanentlylocated at points substantially in the object beams at each viewingpoint for reflecting light from one viewing point to the other, a pairof adjustment coindicant elements and mean including said secondaryreflectors for projecting while ranging and through at least the exactoptical equivalent of all of said aligning, directing and deviatingsystem, light from at least one or the elements into focus forming animage of said one element adjacent to at least an image of the otherelement and for deviating said element image relative to said at leastan image of the other element.

a 17. A coincidence range finder of the type having two spaced viewingpoints at which substantially collimated beams of light are receivedfrom the object being ranged, an optical system for aligning the twoobject light beams, for directing them toward acomparison plane and fordeviating one beam relative to the other, said range finder beingcharacterized by a scale and index constituting a pair of adjustmentcoindi cant elements and means for projecting through at least the exactoptical equivalent of all of said optical aligning; directing anddeviating.

system, light from at least one of the elements into focus forming animage of said one element adjacent to at least an image of the otherelement and fordeviating said element image relative to said at least animage of the other element. B v

18. A range finder according to claim 17 in which said elements arerigidly attached to one another.

19. A range finder according to claim 17 in which said elements are atleast optically in the comparison plane.

20. A range finder according to claim 17 in which said elements are inthe comparison plane.

21. A range finder according to claim 17 in which an eyepiece isincluded for viewing the comparison plane and at least images of saidscale and index are visible through said eyepiece.

22. A range finder according to claim 17 in which is included atransparent element having a flat surface and both of said elements areon said surface.

23. A range finder according to claim 17 in which said elements are insaid field and at the margin thereof.

24. A range finder according to claim 17 in which said comparison planeintersects a surface having a reflecting area adjacent to a transmittingarea and in which said one of the elements consists of a transparentmarking in said reflecting area.

25. A range finder according to claim 1'7 in which said comparison planeis approximately symmetrically located between the two viewing pointsand in which saidoptical system includes a main reflector at eachviewing point directing the beams toward the center of the finder andsaid projecting means includes an auxiliary reflector in front of eachof said main reflectors, oriented to reflect light from the adjacentmain reflector toward the other auxiliary reflector.

26. A coincidence range finder of the type having a housing with twospaced windows in the front thereof at which substantially collimatedbeams of light are received from the object being ranged, an opticalsystem including a reflector behind each window for receiving lightbeams through the windows and for directing them into alignment toward acomparison field, at least one objective for focusing the two beams insaid field and light deviating means for adjusting one beam relative tothe other, said range finder being characterized by a pair of adjustmentcoindicant elements rigidly attached to one another and means includingat least .the exact optical equivslant of all of said alignmentdirecting system and including reflecting meanspermanently located atpoints in front of each of said reflec-' tors for reflecting light fromone window vicinity to the other,'for projecting adjacent to one elementan image of the other element, said element image also being deviated bythe light deviating means. i 1W 27. A coincidence range finder of thetyp'e having a housing with twospaced windows in the front thereof, anoptical systemincluding a reflector behind each window and at least oneobjective for forming in a single comparison field two images of theobject being ranged, means for viewing the images from outside thehousing and light deviating means for adjusting one image: relativetoithe other to bring them into coincidence, said range finder beingcharacterized by auxiliary reflecting'means permanently located atpoints substantially in the path of the object beams at eachviewingpoint'for reflectinglight from one window vicinity to the other and.

two adjustment coindicant elements at least optic'ally in the comparisonfield, one element being viewable substantially directly, light from theother .element being collimated by one objective of the'system, beingreflected by said auxiliary reflectingrn'ieans and being. focusedadjacent. to said one element by one objective of the system,

, said light from the other element also being deviated by the lightdeviating means, whereby any change in the optical system or lightdeviating means which affects the relative position of the two objectimages equally afiects the relative position of said one element andsaid other element image.

28. A range finder of the symmetric-a1 coincidence type having a housingwith two spaced windows in the front thereof, means for defining acomparison field centrally located in the housing, means for viewing thefield from outside the housing, reflecting surfaces in the housing forreflecting light from each window into the comparison field, objectivesof equal focal length axially between the field and each window at theirfocal distances from the field for focusing in the field two images ofthe object being ranged and light deviating means for adjusting oneimage relative to-the other to bring them into coincidence, said rangefinder being characterized by a scale and index integrally attached toone another, both at least optically in the comparison field andconstituting adjustment coindicant elements one of which is visiblesubstantially directly, light from the other element being directed toone objective and collimated thereby, an auxiliary reflector in thevicinity of each of the two windows for receiving this collimated light,for reflecting it from one window vicinity to the other and fordirecting it through the other objective whereby it is brought to focusforming an image-of said other element adjacent to said one element,said light also being deviated by the light deviating means.

29. A range finder according to claim 26 and of the split field type inwhich the field intersects at an angle a flat surface part of which isreflecting to reflect one of the object beams and the rest of which istransmitting to transmit the other object beam, said one element being atransmitting mark in said reflecting part and the other element beingmarked on said transmitting part and in which means are included forsending light to and through said one element only in the direction fromwhich the object beam arrives at said reflecting part. A

aeontzoo 30,'A range finder according to claim 28511:

which; re included crossed reflecting surfaces for receiving the twobeamsgfrom the reflectors behind the windows and for reflecting themparallel to one another, a right an le prism in through the hypotenuseof one of the right angle prisms and in which said one element isinsaid' surface and is illuminated throughv the hypotenuse face of theother right'angle prism.

31. A coincidence range finder of. the orthopsuedo-stereo type havingtwocomparison planes and means for receiving at spaced viewingpoints,beams from the object being ranged for forming in each plane right andleft viewing point images adjacent to one another and light deviatingmeans for deviatingone' image relative to the other, said range finderbeing characterized by a pair of adjustment coindicant.elementsvattached to one another and .means,. including auxiliaryreflecting means permanently located at points substantially in thepaths: .01? the object 2.0 beams at each viewingpoint at leasttheoptical quivalent of all of said imag forming: means;

for proieet ngwmk ran n and from one .oithe 7 elem nts, li ht into focusforming onlmaee -adjacent to at least an image of the; other element.

32. A coincidence range finder of the onthoseudost'ereo type having twocomparison planes nd means for receiving at spaced viewingipolnts;

beams from the ob e t eing ranged-and: for. forming in each plane rightand left viewing 7 p int ima es adiacentito one another-and iightf:

deviating means for deviating one image: relative tothe other, saidrange finder being character.

ized by ascale and an index rigidlyattached to one; another, at leastoptically in one-of the com'- parison planes and constituting adjustment(co, indicant elements and "means, for projecting ad-.

jacent to one of the elements an image of the other element while ran insai pr jecting. means including'the optical equivalentv of all. of

said means for forming images in said one, Ofjjh planes and reflecting.means-permanently located at points substantially in the path of theobject beams at each viewing point for from one viewing point totheother. .l

' JOSEPH .MIHALYI.

reflecting light

